From 8e081d6d061954094fdc78dd13c2c2a16ea10ae6 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Thu, 9 Jun 2022 11:14:47 +0300
Subject: [PATCH] Add geom::smooth_normals

---
 libs/geom/include/psemek/geom/mesh.hpp | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/libs/geom/include/psemek/geom/mesh.hpp b/libs/geom/include/psemek/geom/mesh.hpp
index cb0b9b73..0869abfb 100644
--- a/libs/geom/include/psemek/geom/mesh.hpp
+++ b/libs/geom/include/psemek/geom/mesh.hpp
@@ -123,6 +123,26 @@ namespace psemek::geom
 		return result;
 	}
 
+	template <typename Vertex, typename Index>
+	auto smooth_normals(std::vector<Vertex> const & vertices, std::vector<triangle<Index>> const & triangles)
+	{
+		using vector_type = std::decay_t<decltype(vertices[0] - vertices[0])>;
+		std::vector<vector_type> normals(vertices.size(), vector_type::zero());
+
+		for (auto const & t : triangles)
+		{
+			auto const n = cross(vertices[t[1]] - vertices[t[0]], vertices[t[2]] - vertices[t[0]]);
+			normals[t[0]] += n;
+			normals[t[1]] += n;
+			normals[t[2]] += n;
+		}
+
+		for (auto & n : normals)
+			n = normalized(n);
+
+		return normals;
+	}
+
 	template <typename Index = std::uint32_t, typename Vertex>
 	std::vector<triangle<Index>> triangulate_convex(std::vector<Vertex> const & v)
 	{